Adjust laser focus for PDMS and FEB vat

How can I adjust laser focus to compensate the difference in beam length for PDMS and FEB vat? The level of the FEB vat bottom is 6mm higher. As far as I know the laser is focussed on the bottom of the PDMS vat.

The laser is a diode, it does not need any optical focus system
the laser will and should be focused at any distance

@peopolysupport, please inform yourself about the basics of laser diodes and optics.

Of course, the light from a laser diode is focused on the point. For this purpose, a collimator lens is built into the laser module, which should be set so that the laser beam is focused on the base plate of the VAT.

The beam has its smallest diameter only at the focal point. If you go out of focus, the laser point becomes larger.